docs: def unregisterHandler(self, fh):
  
          """
          Unregister a file descriptor. Clean data, if such operation has been scheduled.
  
          Parameters
          ----------
          fh : int
              File descriptor.
          """
  
          try:
              self.fds.remove(fh)
  
          except KeyError:
              pass
  
          self.lock.acquire()
  
          try:
              self.data.rollover() # rollover data on close.
  
          finally:
              self.lock.release()
  
          if self.closing and not self.fds:
              self.data.close()